Launch vehicles, such as rocket engine propelled vehicles intended for space travel, typically use a liquid propellant that is stored in a storage tank and supplied to engines during takeoff and flight. When the liquid propellant is supplied to the engines, vapor or gases cannot be allowed to enter the engines in large amounts. If vapor or gas is introduced into the engines in sufficient quantities, the gas ingestion may cause a stall or other malfunctioning of the engine that may increase the possibility of engine failure. Additionally, it may be desirable to empty the liquid storage tanks as completely as possible through engine combustion to maximize engine operating time, which may allow for increased vehicle payload.
For example, with reference to FIGS. 1-3, a liquid tank 100 is shown containing a liquid 102 therein. The tank 100 of FIGS. 1-3 does not include an anti-vortex device. An outlet port 104 is positioned at the bottom of the tank to facilitate outflow of the liquid 102. As shown in FIG. 2, as liquid 102 flows through the outlet port 104 and conduit 110, a dip 106 forms in the upper surface 108 of the liquid 102. The dip 106 is formed by inertial forces created by the liquid 102 draining from the tank 100. Due to the formation of dip 106, gas or vapor may be ingested into outlet port 104 at sump 112 and moved through conduit 110, where it is subsequently supplied to an engine (not shown). The dip 106 may increase in size due to a vortex motion of the liquid 102 as it exits through outlet port 104, which also increases the likelihood that gas will be ingested through the outlet port 104.
When there is sufficient liquid 102 in tank 100, as illustrated in FIG. 1, dip 106 may not be present. However, as the liquid 102 drains from tank 100, the dip 106 begins to form as illustrated in FIG. 2. The bottom of dip 106 grows ever closer to outlet port 104 as the liquid 102 drains from tank 100. Finally, as shown in FIG. 3, the dip 106 enters outlet port 104 and may even enter conduit 110, which causes gas to be ingested therethrough. As gas is ingested into the engine (rather than liquid 102), the engine may stall or become damaged.
One known attempt to reduce vapor ingestion uses a screen that encompasses the substantially all of the interior area of the liquid storage tank or at least a portion thereof. In this system, fluid is wicked through the screens by capillary action, and vapor or gas bubbles are prevented from flowing through the screens due to the bubble point pressure of the fluid screen system. However, such screen systems are typically only for storage tanks being used in low gravity and are less useful in environments where higher gravity is present. Additionally, the screen systems typically cannot be used with some liquid propellants such as hydrogen peroxide (H2O2) due to material incompatibility between H2O2 and typical screen materials, for example because the increased surface area of the screens adds more area for chemical reactions causing the liquid propellant to decompose.
Other systems may include vanes extending a distance from a sump of the tank towards the walls of the storage tank. These vanes help bring liquid propellants to the outflow area of the storage tank through capillary action. Furthermore, the vanes may reduce the ingestion of gas bubbles into the engine of the vehicle. The vanes used in known vapor-ingestion-suppression systems are for low gravity applications and cannot provide substantial vapor ingestion suppression at the higher gravity conditions typical of launch vehicles.
A need exists for a device for rockets or launch vehicles under normal or high gravity that will allow for anti-vortexing of the liquid propellant as it leaves a multiple-outlet tank, and to maximize the draining of liquid propellant into the sump and outlets, thereby increasing the efficiency of the storage tanks and decreasing the possible ingestion of gases.